/**
 * A `CancelToken` is an object that can be used to request cancellation of an operation.
 *
 * @class
 * @param {Function} executor The executor function.
 */
export declare class Cancel {
    readonly message?: string | undefined;
    constructor(message?: string | undefined);
    toString(): string;
}
export declare type Canceler = (message?: string) => void;
export interface CancelTokenSource {
    token: CancelToken;
    cancel: Canceler;
}
export declare class CancelToken {
    promise: Promise<any>;
    _listeners?: any[];
    reason?: Cancel;
    static isCancel(obj: any): obj is Cancel;
    constructor(executor: (callback: Canceler) => void);
    /**
     * Throws a `Cancel` if cancellation has been requested.
     */
    throwIfRequested(): void;
    /**
     * Subscribe to the cancel signal
     */
    subscribe(listener: (reason: Cancel) => void): void;
    /**
     * Unsubscribe from the cancel signal
     */
    unsubscribe(listener: (reason: Cancel) => void): void;
    /**
     * Returns an object that contains a new `CancelToken` and a function that, when called,
     * cancels the `CancelToken`.
     */
    static source(): CancelTokenSource;
}